This invention relates to an apparatus for re-energization of the wake of a vane, such as an airfoil, to accelerate dissipation of fluid wakes.
The patents to Hoadley, U.S. Pat. No. 2,650,752; Stephens, U.S. Pat. No. 2,800,291; and my patent, U.S. Pat. No. 4,076,454, relate to apparatus for use in boundary layer control. The patent to Crook, U.S. Pat. No. 1,724,456, relates to aerodynamic control to influence the flow across the wing. The patent to Quinn, U.S. Pat. No. 3,834,834, relates to the use of jets of alternating direction to increase mixing between adjacent streams. My copending patent application, "Mixing Nozzle Trailing Edge Structure", Ser. No. 06/94,622 filed Nov. 15, 1979, now abandoned, relates to mixing a core flow of a turbofan engine with the bypass flow.
Any object placed in a fluid stream produces a wake. If this object is a vane which changes the direction of the fluid stream, it becomes a lifting surface and produces a larger wake because of the increased diffusion occurring on the leeward side. commonly called the suction surface. If, in addition to turning the fluid stream, the vane is in a region of diffusion, the wake will be still larger. This wake consists of fluid of low momentum relative to the vane creating it.
In high-bypass turbofans, it is now common to employ a large streamwise gap between the fan rotor and the following stator vanes in order to minimize the noise produced by the stator vanes chopping the rotor wake.
Also the last stator vane row in an axial compressor, used in an aircraft gas turbine, is followed by a close coupled diffuser and the combustor. Due to the limit on aerodynamic loading of the vanes, more vane rows are required than would be required if the low momentum flow in the wake were not present.